Carotid duplex ultrasonography: importance of standardisation

Background. Carotid duplex ultrasonography (CDUS) is an established non-inv asive tool for assessing patients with suspected carotid bifurcation diseas e. Current trends show an increased dependence on CDUS in recommending pati ents for stroke prevention surgery. The aim of the study was to evaluate ro utine practice in vascular laboratories across 26 countries participating i n The Asymptomatic Carotid Surgery Trial (ACST), and to determine the areas which are in need of future standardisation if CDUS is to be the primary t ool in recommending patients for CEA. Methods. Retrospective. Information was gathered from questionnaires, and 2 2 on-site visits of vascular laboratories between August 1996 to September 1997. Setting. Clinical vascular laboratory practice. Participants. Eligibl e participants were vascular laboratories of ACST collaborators. Measures. Laboratories were compared in 7 categories: ultrasound equipment, operators , experience, protocols, stenosis evaluation, interpretation criteria, and reporting. Results. Information on 117 respondents showed that (i) experience: at leas t one operator in each laboratory had more than 3 years experience; (ii) eq uipment: 88% (103/117) had colour duplex capability; (iii) operators: 54% o f laboratories had exams performed by technologists, 33% vascular surgeons, 28% radiologists, and 35% other. The most significant findings were in (iv ) stenosis evaluation: only 29% (33/117) were using a standardised Doppler angle (this single factor may greatly alter exam results); and (v) interpre tation criteria; with >41 different criteria reported. These specific labor atory variations can affect those patients considered appropriate for CEA. Conclusions. This study highlights the most significant areas for future st andardisation to be Doppler angle and interpretation criteria, if CDUS is t o be a primary tool in recommending patients for CEA, when indicated by cli nical trial results.